1. Field of the Invention
The present invention relates to an SLR camera using light-sensitive film or an electronic image pick-up device so that object images can be taken as latent images on the light-sensitive film or as digital images using the image pick-up device, which can be stored in a recording medium such as a floppy disk or a flash memory.
2. Description of the Related Art
Roll-film SLR cameras using an interchangeable film back which are designed so that different types of film (e.g., 70 mm wide filmxe2x80x94either 120 or 220 roll-film, negative film or positive film) can be selectively used are known in the art. In this type of camera, if an image pick-up device (e.g., a CCD image sensor) can be positioned so that the sensitive surface thereof coincides with the focal plane of the camera body, the camera can be used as digital camera. Accordingly, a digital back (CCD back) has been proposed in which an image pick-up device (e.g., a CCD image sensor) is provided, instead of a light-sensitive film, so that the camera can be used as a digital camera when the digital back is attached to the camera body.
The digital back must be provided in front of the image pick-up device thereof with a filter group which includes, e.g., a filter for filtering infrared rays, a low-pass filter, a protection glass for protecting the image pick-up device from dust and/or another filter or filters. On the other hand, it is necessary for an exposed front surface (light-sensitive surface) of a strip of film to lie in a focal plane formed through the photographic lens when the film back is attached to the camera body. Due to this conventional structure, if the digital back is attached to the camera body instead of the film back, it is difficult to arrange the sensitive surface of the image pick-up device to be positioned in the focal plane. This is because the sensitive surface of the image pick-up device needs to be positioned behind the focal plane by a distance corresponding to the total thickness of the aforementioned filter group positioned in front of the image pick-up device so as to prevent the filter group from interfering with the focal plane shutter provided in the camera body. If the sensitive surface of the image pick-up device is simply arranged to be positioned in the focal plane, the aforementioned filter group will definitely interfere with the focal plane shutter provided in the camera body. This problem can be prevented from occurring if the back focal distance is appropriately adjusted using a relay optical system positioned in an optical path of the photographic lens. However, since the fixing position of the image pick-up device in the digital back, the material of the filter group and/or the thickness of the same varies depending upon the type of the digital back attached to the camera body, it is necessary to change the relay optical system in accordance with the type of the digital back attached to the camera body, which is troublesome and costly. If the protection glass is formed so as to be extremely thin, while the other filter or filters of the filter group are positioned between the focal plane shutter and the photographic lens, such a problem is eliminated in theory. However, this is impractical.
An object of the present invention is to provide an SLR camera which can be selectively used with a film back or a digital back, wherein the aforementioned filter group, which is positioned in front of the image pick-up device provided in the digital back, does not interfere with the focal plane shutter when the digital back is attached to the camera body.
The present invention has been made based on an idea of providing an SLR camera body with a mechanism which moves the photographic lens along the optical axis thereof so as to shift a focal plane of the photographic lens to the sensitive surface of an image pick-up device provided in a digital back when the digital back is attached to the camera body.
In order to achieve the above mentioned object, according to an aspect of the present invention, an SLR camera system is provided, including a camera body; a film back and a digital back that are selectively attached to the camera body, the film back accommodating a light-sensitive film, the digital back having an image pick-up device, wherein the camera body includes a body mount to which an interchangeable lens is detachably attached, the body mount being guided in a direction of an optical axis of the interchangeable lens; a flange-back adjusting mechanism which moves the body mount in the optical axis direction to vary a position of a focal plane formed through the interchangeable lens so as to adjust a flange back; a focusing-screen drive mechanism which moves a focusing screen of the camera body along an optical axis of a finder optical system of the camera body; and an eyepiece drive mechanism which moves an eyepiece of the camera body along an optical axis thereof.
The camera can further include a controller which controls the flange-back adjusting mechanism to vary the position of the focal plane to thereby adjust the flange back; wherein the controller controls the focusing-screen drive mechanism to move the focusing screen to make a matt surface of the focusing screen coincident with an equivalent focal plane which is optically equivalent to the focal plane, and further controls the eyepiece drive mechanism to move the eyepiece to a position where sharp images focused on the focusing screen can be viewed through the eyepiece, in accordance with a type of the digital back attached to the camera body.
The focusing-screen drive mechanism and the eyepiece drive mechanism is driven so as to be associated with the flange-back adjusting mechanism.
The camera body can include a memory in which information on a position of a film surface of the light-sensitive film for when the film back attached to the camera body is stored.
In an embodiment, the controller controls the flange-back adjusting mechanism to make the focal plane coincident with a film surface of the light-sensitive film when the film back is attached to the camera body. The controller controls the flange-back adjusting mechanism to make the focal plane coincident with a sensitive surface of the image pick-up device when the digital back is attached to the camera body.
In an embodiment, the controller starts controlling the flange-back adjusting mechanism to vary the position of the focal plane immediately after the power of the camera body is turned ON.
In an embodiment, the controller starts controlling the flange-back adjusting mechanism to vary the position of the focal plane immediately after either the film back or the digital back is attached to the camera body.
In an embodiment, the flange-back adjusting mechanism includes a rack for moving the body mount in the optical axis direction of the interchangeable lens, and a drive motor for moving the body mount forwardly and rearwardly in the optical axis direction of the interchangeable lens via the rack.
According to another aspect of the present invention, an SLR camera system is provided, including a camera body; a film back and a digital back that are selectively attached to the camera body, the film back accommodating a light-sensitive film, the digital back having an image pick-up device, wherein the camera body includes a body mount to which an interchangeable lens is detachably attached, the body mount being guided in a direction of an optical axis of the interchangeable lens; a finder unit which is attached to the camera body and includes a focusing screen, an erecting optical system and an eyepiece; a flange-back adjusting mechanism which moves the body mount in the optical axis direction to vary a position of a focal plane formed through the interchangeable lens so as to adjust a flange back; and a finder-unit drive mechanism which moves the finder unit along a finder optical axis which extends from a quick-return mirror of the camera body to the erecting optical system.
The camera can further include a controller which controls the flange-back adjusting mechanism to vary the position of the focal plane to thereby adjust the flange back, and further controls the finder-unit drive mechanism to move the focusing screen along the finder optical axis to make a matt surface of the focusing screen coincident with an equivalent focal plane which is optically equivalent to the focal plane.
The finder-unit drive mechanism is driven so as to be associated with the flange-back adjusting mechanism.
The camera body can include a memory in which information on a position of a film surface of the light-sensitive film for when the film back attached to the camera body is stored.
In an embodiment, the controller controls the flange-back adjusting mechanism to make the focal plane coincident with a film surface of the light-sensitive film when the film back is attached to the camera body. The controller controls the flange-back adjusting mechanism to make the focal plane coincident with a sensitive surface of the image pick-up device when the digital back is attached to the camera body.
In an embodiment, the controller starts controlling the flange-back adjusting mechanism to vary the position of the focal plane immediately after the power of the camera body is turned ON.
In an embodiment, the controller starts controlling the flange-back adjusting mechanism to vary the position of the focal plane immediately after either the film back or the digital back is attached to the camera body.
In an embodiment, the flange-back adjusting mechanism includes a rack for moving the body mount in the optical axis direction of the interchangeable lens, and a drive motor for moving the body mount forwardly and rearwardly in the optical axis direction of the interchangeable lens via the rack.
Preferably, the digital back includes a transmitting device for transmitting information on a position of a sensitive surface of the image pick-up device to the controller.
The digital back can include a memory in which the information on a position of a sensitive surface of the image pick-up device used to control the flange-back adjusting mechanism is stored, and a controller which receives the positional information to control the drive motor in accordance with the positional information.
The image pick-up device is preferably a CCD image sensor.
In an embodiment, the digital back further includes a filter group fixedly positioned in front of the image pick-up device.
In an embodiment, the camera body includes a sliding cylinder guided in the optical axis direction and having an axis coincident with the optical axis, the body mount being formed integrally with a front end of the sliding cylinder, wherein the flange-back adjusting mechanism moves the body mount by moving the sliding cylinder in the optical axis direction.
In an embodiment, the camera body includes a sliding cylinder guided in the optical axis direction and having an axis coincident with the optical axis, the body mount being formed integrally with a front end of the sliding cylinder; wherein the rack is formed on the sliding cylinder; and wherein the drive motor includes a pinion on a drive shaft thereof, the pinion engaging with the rack.
According to another aspect of the present invention, an SLR camera system is provided, including a camera body to which a film back and a digital back are selectively attached, the film back accommodating a light-sensitive film, the digital back having an image pick-up device, wherein the camera body includes a body mount to which an interchangeable lens is detachably attached, the body mount being guided in a direction of an optical axis of the interchangeable lens; a first adjusting mechanism which moves the body mount in the optical axis direction to adjust a flange back; a second adjusting mechanism which moves an eyepiece of the camera body along an optical axis thereof; a third adjusting mechanism which moves a focusing screen of the camera body along an optical axis of a finder optical system of the camera body, the third mechanism being linked to the first mechanism and the second mechanism via a first gear group and a second gear group, respectively; and a controller which controls the first, second and third mechanisms to vary a position of the focal plane to thereby adjust the flange back, to move the eyepiece to a position where sharp images focused on the focusing screen can be viewed through the eyepiece, and to move the focusing screen to make a matt surface of the focusing screen coincident with an equivalent focal plane which is optically equivalent to the focal plane, respectively, in accordance with a type of the digital back attached to the camera body.
The present disclosure relates to subject matter contained in Japanese Patent Application No.11-188709 (filed on Jul. 2, 1999) which is expressly incorporated herein by reference in its entirety.